<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    姓名 ： <input type="text" class="myinput" /> <button class="btn">确定</button>
    <script>
        // 获取输入框里的值  元素.value;
        var ele = document.querySelector(".myinput");
        var btn  =document.querySelector(".btn");
        btn.onclick= function(){
            console.log(ele.value);
        }



    </script>
</body>
</html>